What is L-electron capture?
Electron capture is said to take place when a proton located in the nucleus of a radioactive element captures an inner-orbital electron, forming a neutron and emitting an electron neutrino.
The process can be described by this nuclear equation
The electron is usually captured from the K or L electron shells, which correspond to the first and second energy levels.
The K shell corresponds to the principal quantum number n = 1, has 1 subshell, 1s, and can hold 2 electrons. The L shell corresponds to the principal qunatum number n = 2, has 2 subshells, 2s and 2p, and can hold 8 electrons.
Therefore, L-electron capture is said to take place when the captured electron comes from the L shell. Likewise, K-electron capture takes place when the captured electron comes from the K shell.